The present invention relates to microwave transmission lines for transmission of RF signals, and more particularly to a space-saving microstrip or coplanar waveguide transmission line structure particularly useful for hybrid circuits.
Many active RF devices such as active array transmit/receive modules contain DC and control circuitry in close proximity to microstrip or coplanar waveguide RF lines. The RF lines must be separated from all other traces and components to avoid unwanted coupling. The usual technique for accomplishing this is to establish some minimum spacing from the RF line and route the RF line around or through the other lines and components. Sometimes the DC lines are routed underneath the RF line and its groundplane with through-substrate vias and multilayer metallization. These approaches require more circuit board area.
It is therefore an object of this invention to provide a microwave transmission line circuit for use in hybrid circuits which requires less circuit board area, permits close packing of components and leads to smaller and lighter devices.